How to save a group of objects separately for use in other programs?
V2.80 is brilliant with this.


Select the objects in the Outliner 
Right Click on one of the highlighted objects in the Viewport, on the left to the list. 
When the poupup menu comes up select Move to Collection menu item.





That will bring up another popup Menu and click on the + New Collection





Another popup menu will show up, click in the box next to the Name, circled, and type in your new collection name you want. 





In this example named the new collection MyCollection. Click OK button to create it.





The collection is created and can be collapsed or manipulated making individually visible or hidden with the screen and the camera icons next to them. Or select all the objects in the collection with right clicking on the collection name and selecting from the popup menu Select Objects. See first image selected objects and now included in this newly created collection.




The same way you can create collections within collections, called nested collections. 
If you right mouse click on a collection name in the Outliner then from the popup menu you can create a collection with the New menu item and later any selected item can be added to any current collection. In this example adding these 2 additional objects to the MyCollection collection. In this case after step 3 select the desired collection name